The present invention relates to an I.S. (individual section) machine and more specifically to a control for such a machine.
The first I.S. machine was patented in U.S. Pat. No. 1,843,159, dated Feb. 2, 1932, and U.S. Pat. No. 1,911,119, dated May 23, 1933. An I.S. (individual section) machine has a plurality of identical sections. Each section has a frame on which are mounted a number of section mechanisms including blank side and blow side mold open and close mechanisms, an invert and neck ring mechanism, a baffle mechanism, a blowhead mechanism, a plunger mechanism and a takeout mechanism. Associated with these mechanisms is process air used for cooling, for example. Each of the section mechanisms and the process air have to be operated at a selected time in the section cycle.
In the original I.S. machine, devices (valves which operated the mechanisms and the process air, for example) had to be mechanically turned on and off each cycle and the timing process was controlled by a 360xc2x0 timing drum which was a cylindrical drum having a number of annular grooves, one for each valve, each supporting xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d dogs for tripping a corresponding switch associated with a particular valve. The rotation of this mechanical timing drum through 360xc2x0 has always been equated to the completion of one control cycle of the machine or section and accordingly men skilled in this art have always analyzed machine performance in a wrapped cycle, i.e., one that repeatedly cycles from 0xc2x0 to 360xc2x0. When electronic timing replaced the mechanical timing drum, devices were turned on and off by an electronic sequencer which replicated the wrapped 360xc2x0 control cycle of the mechanical timing drum. An encoder defined the angular location of the electronic sequencer, and electronic switches were turned on and off at the same angles as was the case with a mechanical timing drum. A very significant development that greatly enhanced the power of the electronic sequencer was the concept of thermodynamic modes (U.S. Pat. No. 3,877,915) wherein groups of these electronic switches were linked so that they could be simultaneously adjusted. These machine controllers allow the user to electronically adjust the on/off schedule (angle) for the various valves which operate the section mechanisms. This conventional approach does not allow an operator to directly command the machine to achieve desired forming durations (e.g. blank contact time, reheat time). It also does not prevent the user from setting invalid or even potentially damaging sequences in which the mechanisms collide. Only with considerable experience, and process insight can an operator effectively adjust the machine timing with the conventional approach and since skill levels vary greatly, the productivity of the machine can vary substantially.
It is an object of the present invention to provide an improved control system for a glass forming machine which will simplify machine operation and facilitate the tuning of the machine for higher productivity.
Other objects and advantages of the present invention will become apparent from the following portion of this specification and from the accompanying drawings which illustrate a presently preferred embodiment incorporating the principles of the invention.